The present invention concerns advanced epoxy resins and coatings containing same.
Automotive manufacturers are being required by Federal mandate to reduce volatile organic emissions from the paint operations. Increased emphasis on quality has caused manufacturers to install chip resistant coatings between the primer and top coat to resist damage by stone chipping. These stone chips are esthetically unpleasing and can also lead to rusting. Presently used antichip coatings tend to be low in solids and frequently require the use of heating equipment to reduce the viscosity for proper applications.
Coil coating has become an increasingly important method for applying industrial coatings. In this method a metal coil, usually steel or aluminum, is ordinarily coated and the substrate is then post-formed into the final object. Such a coating requires a high degree of flexibility and elongation. Conventional epoxy resins are widely used as primers for these applications. These resins are typically based on the diglycidyl ether of bisphenol A advanced with bisphenol. Typical resins have an epoxide equivalent weight of about 1800-2000. Such resins, however, are lacking where extreme flexibility is required. While resins in the 3000-5000 epoxide equivalent range will give improved flexibility, large amounts of solvent are required to obtain the proper application viscosity. Similar problems are encountered with other applications requiring high flexibility and high formability such as can ends.
The present invention provides high solids coating compositions having improved flexibility and resistance to stone chipping relative to known compositions.